The present invention relates to a new and improved method and apparatus for time-optimizing the performance or occurrence of work at individual operating positions or stations of textile machines.
It is known that for packages which are used as feed material for the so-called warping process, a uniform wound length of yarn is desired, in order to avoid as far as possible losses through remnant or residual yarn lengths, which are no longer usable, on still not quite empty feed packages.
Uniformly wound yarn lengths can be achieved in an open-end spinning method, also referred to in the art as rotor spinning method, by measuring the yarn lengths during the winding operation or procedure by means of a length measuring unit and by interrupting the spinning process per spinning position for a package change operation when a predetermined set or reference yarn length is attained.
The package change procedure can be carried out manually, or by means of stationary package changing and yarn piecing devices which are provided per spinning position or location, or by means of appropriate devices travelling along the spinning positions.
The aforesaid manual variant is not only labor intensive, but demands from the attendant particular skill in yarn piecing, so that the yarn piecings are neither too thin nor too thick. At high rotor speeds, for example over 60,000 rpm, manual yarn piecing is in any event practically impossible.
On the other hand, package changing and yarn piecing devices which are provided for each spinning position constitute, economically overall, an expensive solution.
The economics are improved when there are employed the aforementioned travelling devices. Following an interruption at an individual spinning position, recorded by a control, such devices are, on each occasion, automatically controllably guided to that spinning position for the change operation.
The disadvantage of the last described method step lies, however, in the still relatively long waiting times of the individual spinning positions until the package change operation has been completed, particularly when several packages, which in given circumstances may be spaced apart from each other, must be almost simultaneously changed.
In order to at least partially mitigate this disadvantage, it is suggested in German Patent Publication No. 3,030,504 and the corresponding British Patent Publication No. 2,065,725, to use a length measuring device in combination with a computer unit, in order to send a package changing device to that spinning position at which the package has reached at least approximately the desired length. The length measuring device determines the yarn lengths at a number of spinning positions allocated to it and communicates these lengths continuously to the computer unit in which the length values are stored and respectively compared with the set or reference value.
When a package reaches a predetermined maximum difference in length from the set value, then the computer unit orders the movement of the package change device to this package as a precautionary measure, so that when the yarn length corresponding to the set value is reached, the package change procedure is initiated. The removal of the full package is followed by the insertion of an empty bobbin and piecing-up of the yarn end separated from the full package. The removal of the full package, the insertion of the empty bobbin, and the piecing-up of the yarn end on the empty bobbin are also concisely called "doffing", and the device which carries out this "doffing" operation is concisely called a "doffer".
The aforesaid maximum difference in length corresponds to the longest necessary travelling time of the doffer including the time for the doffing itself.
The disadvantage of this method lies in the long waiting time until the package changing procedure occurs when there prevail only short required travelling times. This disadvantage results in a severely limited frequency of package changing.